“People like to have an enemy, and vilifying non-native species makes the world very simple,” said ecologist Mark Davis of Macalester College. “The public got sold this nativist paradigm: Native species are the good ones, and non-native species are bad. It’s a 20th century concept, like wilderness, that doesn’t make sense in the 21st century.”

Most are actually benign, relegated to a lower-class status that reflects prejudice rather than solid science, write the authors. Non-natives are assumed to be undesirable, and their benefits go ignored and unstudied.

‘To value the nature we actually have, and are creating, we need to think broadly…. Nature is something we create now.’

As examples of unfairly maligned invaders, the authors mention Australia’s devil’s claw plants, subject to a 20-year-long plant hunt that’s done little to contain a species that may cause little ecological disturbance. In similar fashion, tamarisk trees in the U.S. southwest have been targeted for 70 years by massive eradication programs, but are now seen as providing important bird habitat. Ditto the honeysuckle, banned in many U.S. states, but providing an apparent boost to native bird biodiversity.

“Classifying biota according to their adherence to cultural standards of belonging, citizenship, fair play and morality does not advance our understanding of ecology,” wrote the essay’s authors. They also consider ecological nativism to be hypocritical — nobody’s complaining about lilacs or ring-necked pheasants — and a form of denialism: In a globalized, human-dominated world, plants and animals will get around.

“Most human and natural communities now consist both of long-term residents and of new arrivals,” they wrote. “We must embrace the fact of ‘novel ecosystems.’”

Many other ecologists, however, were dismayed by the essay. David Pimentel of Cornell University said many invasive benefits are indeed recognized: Ecologists hardly complain about corn and other non-native crop plants. He said Davis and colleagues cherry-picked their examples.

“This article … is biased and is not a fair representation of the risks and benefits,” said Pimentel, who has estimated invasive species damage in the U.S. at between $100 billion and $200 billion. His point was echoed by Jessica Gurevitch, an ecologist at the State University of New York Stony Brook. “I think they downplay some of the problems and uncertainties,” she said. “That we should just get used to it, is not correct.”

Davis said that non-native species need to be addressed on a case-by-case basis. “We’re not saying, ‘Everything is okay, let’s open the doors,'” he said. “What’s frustrated us is that the actual data has often been misrepresented. People have heard that non-native species represent the second-greatest extinction threat in the world, and it’s just not true.” Davis noted that in many places, non-native species actually increase total biodiversity.

But a different criticism came from David Lodge, a Notre Dame ecologist who studies Great Lakes Asian carp invasion. Those potentially fisheries-wrecking fish also embody what some biologists call ‘the homogecene’: Habitat disruption and non-native species flow reduce ecological uniqueness. Even as local biodiversity increases, each locale may come to resemble the next. “The researchers focus on biodiversity as the fundamental good. But what if that’s not the goal?” said Lodge.

There is, however, a common ground for these arguments: Each reflects the basic fact that, early in the 21st century, humanity is the driving force of nature on Earth. Whether species are classified as native or non-native, whether they’re accepted or rejected, reflects a choice. Philosophy guides stewardship, and stewardship is global.

“Humans are managers, humans are gardeners. We make the decisions about what species we want, and where,” said Lodge.

“To value the nature we actually have, and are creating, we need to think broadly,” said earth scientist Erle Ellis of the University of Maryland, Baltimore County, who invented the term ‘anthrome’ to define the hybrid human-natural systems that now dominate Earth’s surface. “Nature is something we create now.”

Images: Tamarisk trees along the Colorado river (Steven Damron/Flickr)